Vulcanization accelerators for fluorinated polymers and compositions thereof



United States Patent 3,502,628 VULCANIZATION ACCELERATORS FOR FLUO- RINATED POLYMERS AND COMPOSITIONS THEREOF Arthur Livingston Barney and Wolfgang Honsberg, Wilmington, Del., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Continuation-impart of application Ser. No. 661,230, Aug. 17, 1967. This application May 22, 1968, Ser. No. 736,786

Int. Cl. 'C08f 45/72 U.S. Cl. 260--87.7 Claims ABSTRACT OF THE DISCLOSURE The acceleration of the vulcanization of saturated, fiuorinated polymers by the use of tropolone and 1,10- phenanthroline. The accelerators enable a more rapid cure with conventional amine-based vulcanization systems and also enable a satisfactory rate and state of cure with weakly basic bis-nucleophiles otherwise incapable of adequately curing fluorinated polymers.

CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation of applicants copending application Ser. No. 661,230, filed Aug. 17, 1967, now abandoned.

BACKGROUND OF THE INVENTION Field of the invention This invention relates to the vulcanization of fluorinated polymers and, more particularly, it relates to vulcanizable compositions containing such polymers.

Description of the prior art The vulcanization of saturated, fluorinated elastomeric polymers is well known. A wide variety of amine-based vulcanization systems have been developed. It is frequently desirable, however, to accomplish the state of cure desired in a shorter time. Moreover, it is sometimes desirable to be able to use as curing agents certain compounds presently somewhat unsatisfactory for that purpose either from a time-delay standpoint or from the ultimate state of cure obtainable therewith.

SUMMARY OF THE INVENTION In the vulcanization of saturated, fluorinated elastomeric polymers, the improvement of adding to said polymers before vulcanization up to about 5 parts, per 100 parts of polymer, of the compounds tropolo-ne or 1,10- phenanthroline.

DETAILED DESCRIPTION OF THE INVENTION This invention is applicable to saturated interpolymers of vinylidene fluoride (VF with other fluorine-containing ethylenically unsaturated monomers copolymerizable therewith. Typical of the latter are hexafluoropropene (HFP), tetrafluoroethylene (TFE), perfluoroalkyl perfluorovinyl ethers [particularly where the alkyl radical contains from 1 to about 4 carbon atoms such as perfluoro(methyl vinyl ether) and perfluoro(propyl vinyl ether)], trifluorochloroethylene, and pentafluoropropylene. Of particular interest are the vinylidene fluoride/ hexafluoropropene copolymers containing from about 70 to about weight percent vinylidene fluoride and about 30 to about 70 weight percent hexaflporopropene (see Rexford, U.S. Patent 3,051,677). Other important polymers are the terpolymers of vinylidene fluoride/hexafiuoropropene/tetrafluoroethylene wherein the monomer units are present in the following mole ratios: about 3 to 35 (preferably 15 to 25) weight percent tetrafluoroethylene units and about 97 to 65 (preferably 85 to 75) weight percent vinylidene fluoride and hexafluoropropene units, the latter two being present in a weight ratio of from about 2.5 :1 to 0.5 :1 (see Pailthorp and Schroeder, U.S. Patent 2,968,649).

Other vinylidene fluoride polymers and their preparation are disclosed in Dittman et al., US. Patents 2,738,343 and- 2,752,331; Hanford and Roland, U.S. Patent 2,468; 664; Brubaker, U.S. Patent 2,393,967; and Honn et al., U.S. Patents 2,833,752 and 2,965,619.

Fluorinated polymers not derived from vinylidene fluoride such as interpolymers of tetrafluoroethylene with perfluoro(alkyl vinyl ethers) can be employed.

The compounds 1,10-phenanthroline and tropolone and their preparation are well known to those skilled in the art.

The amine-based vulcanization of saturated, fluorinated polymers, especially V1 copolymers, is well known to those skilled in the art. Frequently used are the organic aliphatic diamines, e.g., ethylene diamine or hexamethylene diamine, or their carbamates. The subject has been discussed and explained in publications, such as J. F. Smith, The Chemistry of vulcanization of VitonA Florocarbon Elastomer, Proceedings of International Rubber Conference, pp. 575-581, Washington, November 1959; and Paciorek et al., Mechanism of Amine Crosslinking of Fluoroelastomers, J. Poly. Sci., vol. XLV, pp. 405, 413 (1960). Although spoken of as amine-based curing, the amines may be used as carbamates, hydrochloride-s, oxalates, or reaction products with hydroquinone. Many amine-based systems have been devised to produce special effects using primary, secondary and tertiary amines, aliphatic and aromatic, alone or in combination with other amines. Hydrazine andits derivatives have also been used in such systems.

Amine-based vulcanizations are the subject of many patents, e.g., West, U.S. 2,793,200; Rugg, U.S. 2,933,481; West, U.S. 2,979,490; Smith, U.S. 3,008,916; Griflin, U.S. 3,041,316; and Davis et al., U.S. 3,071,565.

The accelerators of this invention also enable the rapid and satisfactory vulcanization of saturated, fluorinated polymers by using poly(nucleophiles) in a basic system. Representative are bis(nucleophiles) such as dihydroxy aromatic compounds, such as 2,2-bis(4-phenylol)propane (bisphenol-A), 2,2-bis(4-phenyl0l)perfluoropropane (bisphenol AF), resorcinol, 1,7-dihydroxynaphthalene, 4,4- dihydroxydiphenyl, 4,4-dihydroxystilbene, 2,6-dihydroxyanthracene, hydroquinone, or their alkali or alkaline earth metal salts; lower aliphatic diols, e.g., 1,3-propanediol and 1,6-hexanediol; dithiols, such as p-xylyldithiol; various weakly basic aromatic diamines like methylenedianiline, 0-, mand p-phenylenediamine; and bis-hydrazinium oxalate. Other polynucleophiles include pentaerythritol, diphenylsilanediol and 1,3,5-trihydroxybenzene.

The various nucleophilic groups need not be the same.

The accelerators of this invention are normally used in the presence of basic divalent metal oxides such as MgO, CaO, ZnO, PbO, Pb O BaO and basic metal hvdroxides such as Mg(OH) Ca(OH) and Ba(Ol-I) The latter may be used to form complexes with the crowns before use.

This invention is particularly useful because it offers routes to faster vulcanization with lower amounts of polyamine compound, thus reducing cost and reducing the amounts of excess polyamines which are believed to be deleterious for best heat resistance. The accelerator compounds of this invention also enable the use of various materials as curing agents which could not be satisfactorily employed alone. It has been found that the accelerator &. Procedure for compounding, vulcanizing and' testing fluorine-containingcopolymers On a cool, 2-rol1 rubber mill, l parts of a copolymer )f vinylidene fluoride and hexafluoropropene containing 30 and 40 Weight percent, respectively, are compounded vith 20 parts of medium thermal carbon black and 15 )arts of maguesium'oxide. Except as noted 135 parts af this composition are used for further compounding with the vulcanizing agents and accelerators described n the examples. The compositions are sheeted off the nill and specimens for physical testing are prepared. An iscillating: disc rheometer (ODR) is used to determine apidity of cure after selected times that a test piece is leld at curing conditions. The ODR measures the relative IiSCOSllIY of an elastomer by oscillating (e.g., at 900 :.p.m.) a grooved conical disc through 3 degrees of arc vhile pressed tightly between two test pieces. The amount )f torque required to oscillate the, disc is reported as the measure of viscosity. 7;

Vulcanizates are prepared by compression molding of tppropriate samples in a press for 30 minutes at 163 C. ollowed by removing them from the mold and post- :uring' by heating in an air oven to 264 C. over a 4- mm period and then an additional 24 hours at this tem- Ierature.

EXAMPLE .EQHESTERTNG COMTOUNDSAS ACCELERATQRS FOE HEXAMETHYLENEDIAMINE (EMDAC) Procedure A is followed using HMDAO (1.5 parts) and the following ccelerators: 7

'arts of 1,10-phenanthroline i *0 5 'arts of tropolone 0 V 5 Oscillating disc rheometer at:160 C. (inch pounds of torque) 40 titer 2.5 minutes- 3 64 9. titer 5 minutes 10 94 29 titer 10 minutes 38 104 67 titer 20 minutes 112 83 Outside the invention-ior comparison only.

1 Having an iodine number of about 43.

is not limited to the specific emhodimentsthereof axcept as defined in the appended claims, and all changes which come within the meaning and range of equivalence are intended to berembraced therein.

We claim:

1. In the vulcanization of saturated, fiuorinated elastomeric polymers; the improvement of adding to said polymers before vulcanization an elfective amount up to about 5 parts, per 100 parts of polymer, of the selected compounds tropolone or 1,10-phenanthroline. a

2. The process as defined in claim 1 wherein said po ymers are copolymers of vinylidene fluoride with at least one other fluorinated monomer copolymerizable therewith. r

:3. The process as defined in claim 2 wherein said vulcanization improved is :an amine-based vulcanization conducted in the presence of a basic divalent metal oxide.

4. The process as defined in claim 2 wherein the compound selected is .tropolone.

5. The process as defined in claim 2 wherein the compound selected is 1,10-phenanthroline.

6. Aavulcanizable, saturated, fluorinated elastomeric poly-met containing an effective amount to about 5 parts, per 100.:parts of: polymer, of the selected compounds tropolone or 1,10-phenanthroline. i

7. A vulcanizable, saturated, fluorinated elastomeric polymer as defined in claim 6 wherein said polymer is a copolymer of vinylidene fluoride with at least one other fluorinated monomer copolymerizable therewith.

8. A vulcanizable, saturated, fluorinated elastomeric References Cited UNITED STATES PATENTS 6/ 1962 Smith 260- 45] i JOSEPH L. SCHOFER,"Primary Examiner JOHN KIGHT, Assistant Examiner US. Cl. XaR. 

